A number of systems and methods are known for determining the 2D or 3D geometry of scene. Typically, this is done with specialized equipment such as ranging devices or stereoscopic cameras.
To determine 3D geometry from monocular images is more difficult. Shape-from-shading techniques assume that the scene has some known reflectance properties, such as Lambertian, Hapke, etc. Structured light is frequently used to determine 3D geometry because it is robust to reflectance and surface geometry. One method for active ranging uses color-coded structured light, K. L. Boyer, A. C. Kak, “Color-encoded structured light for rapid active ranging”, IEEE Trans. Pattern Anal. Mach. Intell., 9(1), 1987, pp. 14-28. Another method uses multi-stripe inspection, J. A. Jalkio, R. C. Kim, S. K. Case, “Three dimensional inspection using multistripe structured light,” Optical. Engineering, 1.985, pp. 966-974.
The main idea is to project a structured pattern of light with known geometric properties into a scene. Then, an analysis of the distortions induced on the pattern, as seen in images acquired of the scene by a camera, can be used to determine the 3D geometry of the scene, R. J. Valkenburg and A. M. Melvor, “Accurate 3D measurement using a structured light system,” Image and Vision Computing, 16(2):99-310, February 1998, D. Scharstein, R. Szeliski, “High-accuracy stereo depth maps using structured light,” IEEE Comput. Soc. Conf. on Computer Vision and Pattern Recognition (CVPR03), vol. 1, pp. 195-202, June 2003, and Joaquim Salvi, Jordi Pagès, Joan Batlle. “Pattern codification strategies in structured light systems,” Pattern Recognition 37(4): 827-849, 2004.
However, using structured light in user interactive application has problems. The structured light changes the appearance of the scene. Therefore, it is desired to determine 3D geometry using a structured light pattern that is not visible to the user.